Future optical disc formats will demand local storage on the player instruments. This is because content, carried e.g. on a read-only optical disc, very soon becomes outdated, and the content producing studios intend to increase the attractiveness of their products. Local storage on player instruments provides the ability for adding further amendments and most recent supplements to the optical disc content, without increasing the disc production costs, as would be necessary for writable discs. When connected to the Internet, it is possible to download supplements to the local storage, or to replace content of the read-only disc. E.g. it is possible to replace an outdated movie trailer by a new one, or to supplement disc content by further audio or subtitle tracks. Also executable code, like a game bound to a particular optical disc, can be downloaded and run on the instrument while the associated disc is in the player.
A problem arising with this technically applicable possibility is the protection of copyrights bound to disc and supplement data. It is desirable to preserve copyrights in such a way that downloaded supplement data can be exclusively used when the related optical disc is inserted within the playback instrument. Any usage of supplement data stemming from the content provider, also a usage independent from the dedicated optical disc, should be under the control of the content owner, i.e. the content provider. The content provider wants to be sure that all of his content, whether it comes from the disc or it has been stored on local storage, cannot be used illegally or accidentally without having the disc, or in any combination with other content.
Usually data from local storage and from optical disc storage are mounted together into a virtual file system (VFS) within a player. This is done only once, namely when inserting the disc and starting the first application. Any further application start is based upon that virtual file system. This is a security risk, because even when data access is restricted, content becomes visible to foreign applications.